In gas turbine engines, compressed air discharged from a compressor section and fuel introduced from a source of fuel are mixed together and burned in a combustion section. The mixture is directed through a turbine section, where the mixture expands to provide rotation of a turbine rotor. The turbine rotor may be linked to an electric generator, wherein the rotation of the turbine rotor can be used to produce electricity in the generator.
Gas turbine engines using annular combustion systems typically include a plurality of individual burners or fuel nozzles disposed in a ring about an axial centerline for providing a mixture of fuel and air to an annular combustion chamber disposed upstream of the turbine section of the engine. The combustion process of the burners will interact in the combustion chamber since all burners discharge the combustible mixture to the single annulus. Consequently, combustion processes in one burner may affect the combustion processes in the other burners. Other gas turbines use “can-annular” combustors, wherein individual burner cans feed hot combustion gas into respective individual portions of the arc of the turbine inlet vanes. Each “can” includes a plurality of main burners disposed in a ring around a central pilot burner, as illustrated in U.S. Pat. No. 6,082,111.
During operation of the burners, the formation of combustion oscillations can occur, which are also known as combustion chamber humming. The combustion oscillations may be caused by an interaction between the fuel and air mixture. Combustion oscillations can cause an increased production of noise and may also increase mechanical and thermal loads on walls surrounding the combustion chamber and on other components in and around the combustion section. In modern engines, temperatures in the combustion section have increased to increase the output power of the engine, thus exacerbating the problems associated with combustion oscillations. Because “can-annular” systems have several independent combustion zones, thermoacoustic problems, including combustion oscillations, can be tuned out on an individual basis and can be predicted by testing only one “can”.
However, it would be desirable to design a non-can-annular system that could be tuned on an individual basis such that thermoacoustic problems could be predicted by testing only a portion of the system.